JPH0759807B2 - Improvement method for soft ground - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for improving soft ground.

<< Prior Art >> For example, when embankment is constructed on soft ground, it may be pulled up at the peripheral edge and subside, or conversely, it may rise due to a heaving phenomenon due to lateral displacement.

If lateral displacement such as subsidence or swelling of this kind occurs beyond the boundary of the site, it will cause trouble to the neighborhood.

Therefore, as a measure to prevent this deformation, conventionally, by constructing sand compaction piles that reach the supporting ground in the ground, by placing steel sheet piles, or by the deep mixed soil construction method, the ground corresponding to the embankment and the peripheral ground are I was trying to cut the edge of the border.

<< Problems to be solved by the invention >> However, in the sand compaction method,
There is a risk of moving the surrounding ground during construction, and the risk of moving the surrounding ground during the placement and withdrawal of steel sheet pile, which is not preferable when the site to be improved and the neighborhood are close. .

On the other hand, in the deep-mixed mixed soil construction method, although there is no ground change during construction, consolidation does not proceed depending on the property such as when the target ground is corroded soil or organic soil, and there is a restriction on the target ground. there were.

Furthermore, a large machine is required for any of the construction methods,
There were also problems in terms of construction cost and construction period.

The present invention solves the above-mentioned drawbacks, and an object of the present invention is to provide a ground improvement method which is cheaper than the conventional method and can reliably prevent the surrounding ground from sinking.

<< Means for Solving the Problem >> In order to achieve the above-mentioned object, the present invention, in the stage before the embankment is constructed on the upper part of the soft ground, is soft along the boundary between the improved area of the soft ground and the surrounding area. A pressure-resistant hose with a hole is vertically penetrated into the ground, and muddy water such as bentonite is injected into the pressure-resistant hose to form the first pile column, and the outside of the column is also left. A column-shaped columnar column made of a hardened material outside the second column-shaped columnal column by injecting and filling a pressure-resistant hose into the soft ground along with the curable fluid inside the pressure-resistant hose. Is formed.

<< Action >> The first pile column in the shape of a mud cake, which is formed when water in muddy water such as bentonite deviates, becomes slippery, and when the improved area subsides due to earth pressure of the embankment, this column Slip in the row part and sink vertically along the peripheral area. Further, the second pile-shaped columnar row made of the hardened body of the hardenable fluid on the outer side receives the lateral pressure due to the change with time of the subsidence,
Prevent the flow of ground to the surrounding area.

Further, as a machine for punching a pressure resistant hose with holes and a machine for driving a pressure resistant hose, a penetrating machine used in the conventional draining method can be diverted.

<< Embodiment >> An embodiment of the present invention will be described in detail below with reference to the drawings.

1 to 4 show a ground improvement method according to the present invention.

In this method, first, before the embankment is constructed, as shown in FIG. 1 (a), along the boundary between the improved area A of the soft ground E and the surrounding area B, the soft ground E is flexible and liquid-tight. A cylindrical mandrel 12 containing a flexible pressure-resistant hose 10 is inserted almost vertically.

There are holes in places of this pressure-resistant hose 10,
A tip cone 14 is attached to the lower end of the mandrel 12 to prevent dirt and sand from entering and to prevent the mandrel 12 from rising when pulled out.

For the penetration work of the mandrel 12, the conventional paper drain penetration machine can be diverted.

When the mandrel 12 reaches the supporting ground E1 below the soft ground E, the pulling out is started.

When the mandrel 12 is pulled out, earth pressure acts on the outer peripheral portion of the tip cone 14 so that the tip cone 14 is pulled out from the mandrel 12 while holding the pressure resistant hose 10 at its depth position.

When the mandrel 12 is completely pulled out, the pressure-resistant hose 10
As shown in FIG. 6C, the support ground E1 is left in the soft ground E in a state of extending vertically from the ground surface to the ground surface.

After the pulling out of the mandrel 12 is completed, the upper end of the pressure resistant hose 10 is cut off at the ground surface as shown in FIG. 1 (d).

Next, an injection pipe 18 connected to the pump 16 is inserted into this opening, the periphery is bound with a band 20, and muddy water 22 such as bentonite is injected into the pressure resistant hose 10 through the pump 16.

When the muddy water 22 is injected, the pressure-resistant hose 10 expands so as to push away the surrounding soft ground E as shown in FIG. 1 (e), and at the same time, a part of it is exposed to the outside through the hole formed in the pressure-resistant hose 10. It leaks and forms a layer around the periphery.

After injecting a predetermined amount, the upper end of the pressure-resistant hose 10 is closed with a band 20 to finish the construction for one line.

By repeatedly injecting the pressure-resistant hose 10 and injecting the muddy water 22 along the boundary one after another, the boundary between the improved area A and the surrounding area B is formed by the water in the muddy water such as bentonite deviating with the passage of time. It is divided by the first row of columns of mud cake 24.

The first row of columns of mud cake 24, as shown in FIG.
The ring-shaped mud cake layer 24a generated by the leakage of the pressure-resistant hose 10 to the outer peripheral portion forms a continuous column.

It should be noted that what is shown in FIG. 2 is the initial state, and the hose 10 becomes flat over time due to the action of earth pressure.

Further, after this work or before that, as shown in FIG. 4, a hardened material such as mortar and cement slurry is formed in the soft ground E on the outer side of the first column row of the mud cake 24. A second column row of hardened bodies 26 is formed.

The hardened body 26 is applied in the same process and order as the above.

That is, after penetrating into the soft ground E of the pressure-resistant hose 10, a curable fluid made of mortar, cement slurry or the like is filled into the inside of the soft ground E instead of the muddy water, and the cured body 26 for one line is constructed by curing. To complete.

By performing this work one after another along the outer side of the column row of the mud cake 24, the second column row of the hardened body 26 can be obtained. If the pressure-resistant hose 10 has no holes, the hardened body 26 will be a linear column, and
When 10 is perforated, it hardens into a branch shape along the outside and forms a tree-shaped column array.

The second pillar row of the hardened body 26 is, for example, as shown in FIG. 3 (a), a sub-sequential row construction is performed at predetermined intervals along the boundary portion, and adjacent rows are staggered. They may be arranged in a line or may be densely arranged in a line as shown in FIG. 3 (b).

After the above work is completed, as shown in FIG. 4, if the embankment 28 is applied to the above-ground portion of the improved area A, the operation is completed.

When the construction is completed, the soft ground E in the construction area A is submerged by the load of the embankment 28 as shown by the imaginary line in the figure, and the subsidence tends to cause the subsidence in the surrounding area B to cause subsidence. Area improved by the columns of cake 24
The ground E of the ground slips vertically with the mud cake 24 and blocks the displacement at this portion, which prevents the subsidence phenomenon from being transmitted to the outside of the first column row of the mud cake 24.

Further, when all the slippage at this portion cannot be absorbed, the second column row of the hardened body 26 on the outer side cuts off the gap with the surrounding area B.

Further, the ground E, which has been consolidated due to the subsidence phenomenon of the improved area A, tends to generate a lateral pressure toward the surrounding area B and flows, but this lateral pressure is received by the second column row of the hardened body 26, As a result, the bulging phenomenon of the peripheral area B can be prevented.

By the above action, the surrounding area B maintains the flat state before construction.

<< Effects of the Invention >> As described in detail with reference to the above examples, in the improved method for the soft ground according to the present invention, the inside and outside partitioned by the mudcake-shaped first pile-shaped pillar row become slippery, When the improved area is subsided by the earth pressure of the embankment, vertical sliding occurs in the first column row portion, and the pull-in subsidence phenomenon is prevented. Further, the second pile-shaped columnar row made of the hardened body on the outer side receives lateral pressure due to the time-dependent change of the subsidence and prevents the ground from flowing to the surrounding area, so that the uplift of the outer ground is also prevented.

Further, as the machine for driving the pressure-resistant hose, the penetrating machine used in the conventional drain construction method can be diverted, and there is an advantage that the construction can be completed easily and in a short time as compared with the conventional construction method.

Therefore, according to the present invention, it is suitable as a ground improvement method for constructing an embankment while preventing influences such as subsidence and swelling of the surrounding ground.

[Brief description of drawings]

1 (a) to 1 (e) are cross-sectional explanatory views showing a procedure for constructing a mud cake in the method of the present invention, and FIG. 2 is a cross-section showing a column of the mud cake along line II-II in FIG. 1 (e). FIGS. 3 (a) and 3 (b) are plan views showing a state where the hardened body is placed, and FIG. 4 is a cross-sectional view for explaining a state where the embankment is completed and a subsequent change. E ... Soft ground 10 ... Pressure hose 12 ... Mandrel 22 ... Mud 24 ... Mud cake 26 ... Hardened body 28 ... Embankment A ... Improved area B ... Surrounding area

Claims (1)

[Claims] 1. A pressure-resistant hose having a hole is vertically inserted into the soft ground along the boundary between the improved area of the soft ground and the surrounding area before the embankment is constructed on the soft ground. In addition, while pouring mud water such as bentonite into the pressure-resistant hose to form the first pile-shaped column row while leaving the pressure-resistant hose, the pressure-resistant hose penetrates into the soft ground along the outer side of the column row and is left behind. A method for improving soft ground, characterized in that the second pile column is formed by injecting and filling a curable fluid into the pressure-resistant hose in the above state.